Puberty is increasingly recognized as an important yet understudied period of brain maturation. Prepubertal and adult male hamsters differ in behavioral and physiological responses to chemosensory and hormonal stimuli, suggesting that a fundamental change in brain function occurs during puberty. This proposal tests the hypothesis that development of male sexual behavior during puberty results from neuroanatomical maturation of the forebrain mating circuit. Aim 1 tests whether pubertal changes in dendritic elaboration are associated with the pubertal development of male sexual behavior. The failure of prepubertal males to show sexual behavior with the appropriate chemosensory and hormonal priming also suggests that these signals may not be integrated and communicated within brain regions mediating sexual behavior. Aim 2 tests whether efferent and afferent neurons of Me are activated by chemosensory cues similarly in prepubertal and postpubertal males. A basic understanding of the processes controlling pubertal brain development provides a timely foundation for future studies of self-administered steroids, disease states, or environmental endocrine disrupters.